1. Technical Field
Example embodiments of the present invention relate in general to provision of multimedia services, and more specifically, to a transmitter and a receiver for providing a multi-layer multimedia service, and a method thereof.
2. Related Art
With the ultra-high speed of wireless networks and the Internet, video-based multimedia content services have been popularized in a broadcasting and telecommunication converged environment, such as video streaming, mobile broadcasting, IPTV, etc. In particular, with the introduction of mobile terminals such as smart phones, demands for mobile multimedia services are rapidly increasing.
Multimedia services require provision of various kinds of multimedia information having different information characteristics. Also, various kinds of terminals capable of using multimedia services and various kinds of service qualities capable of implementing for each terminal are provided.
In order to efficiently cope with such diversity, service scalability is needed. Also, in mobile broadcasting, since the states of channels continue to change, graceful degradation should be ensured in order to avoid abrupt degradation of service quality.
Since the transmitter of a broadcasting system has no information (kind of terminals, required service qualities, channel states, etc.) about terminals, it is difficult to provide multimedia services efficiently according to users' requirements.
That is, most of existing broadcasting systems have been designed in consideration of a terminal in the worst conditions. For example, eMBMS of 3GPP has adopted QPSK modulation and Single Input Single Output (SISO) transmission scheme having the lowest transmission efficiency in consideration of the case where a terminal has only one reception antenna and the channel state is very bad.
However, the approach has a problem that even though terminals having a plurality of reception antennas and being in a good channel environment can receive information at a high transmission rate, the terminals cannot receive high-quality multimedia services due to a limited amount of transmission information. Accordingly, in order to efficiently provide multimedia services, a transmitter has to provide high-quality multimedia services, and a terminal has to decide quality of service according to its performance and channel state.
Scalable video coding (SVC), which is a representative technique for ensuring scalability, has been adopted as a standard by many Standardization Organizations. In the SVC, an input signal is represented as multi-layer information having different information priorities.
Multimedia information encoded by the SVC scheme is mainly transmitted by a layered modulation (LM)-based transmission method. In the LM-based transmission method, a modulated base layer and an enhanced layer are transmitted at the same time. For example, AT-DMB and MediaFLO use 16QAM to transmit a modulated base layer and an enhanced layer at the same time. However, in the case of transmitting two or more layers, reception performance is degraded due to an increase of inter-layer interference. Also, in the LM-based transmission method, coverage rapidly decreases since power allocated to the base layer is reduced as the number of layers increases.
A transmitter that provides high-quality multimedia services is required to transmit information at high speed, and for fast transmission, it is suitable that a Multiple Input Multiple Output (MIMO) technology is used. In order to transmit information according to the MIMO technology, the number of reception antennas is required to be equal to or more than the number of transmission antennas. However, in conventional mobile broadcasting, in many cases, since the number of reception antennas of a terminal is less than the number of transmission antennas of a base station, it is difficult to use the MIMO technology.